Roof and waterproofing membranes and linings have long been used to protect buildings, to contain water in ponds and decorative water features, to prevent leaching of contaminants from landfills, and for other purposes. While these membranes have utility, leakage through the membranes is an ongoing problem. The efforts to contain and locate leakage have resulted in the rise of specialized consultants, air and vacuum testable membranes, and, in recent history, electrical testing methods that not only determine if a leak is present in a membrane system, but where the leak is located.
Leakage in existing roofs is a particular problem, especially when the roof has a nonconductive element at the bottom of the roofing envelope next to the deck, such as a vapor barrier or a secondary roofing membrane. In these cases, water leaking into the roofing envelope can saturate the insulation and other elements in the envelope without actually leaking into the building because the lowermost membrane acts as a barrier to the water. In time, water might run into the building via penetrations, such as vent stacks, curbs for mechanical equipment, conduits, etc., through the roofing envelope and be visible from underneath. By this time, corrective action may be as extensive as cutting cores in the roofing envelope to determine the extent of water damage; removing a large portion of the roof; performing infrared or other tests to indicate the current status of the roofing envelope; etc.
Additionally, when the roofing envelope becomes saturated with water, a portion of the planned energy efficiency from the roofing envelope is lost. The building structure may also experience the corrosive effects of water, therefore compromising its penetrations. Unbeknownst to anyone, this process is occurring in thousands of roofs across North America and, indeed, in the built environment anywhere in the world.
There are methods that have been developed to address the above described problems including manual methods, such as capacitance testing, infrared scanning, and moisture probing. In addition, there are automatic systems driven by computers with sensors built into or retrofitted into the non-conductive insulation and other non-conductive materials which comprise the roofing envelope.
One known method of placing such an automatic system into a non-conductive envelope is to install relative humidity sensors in the roofing envelope, where the sensors measure humidity and temperature. An array of such sensors can give a representation of moisture conditions in a roofing envelope. Such a system is provided by Progeo GmbH of Germany and other vendors, and these systems have been used on projects in the United States. Such systems are limited in that the sensors require a certain amount of free air around them in order to determine the ambient moisture content of any part of the roofing envelope, and each sensor is only one point, measuring the relative humidity of a very small area around its location. Further, there is no guarantee that any air will circulate in the roofing envelope, and if the free flow of air is cut off, especially given the impermeable nature of closed-cell insulations in today's roofing envelopes, the sensors will not be able to sense variations in moisture, but only temperature changes.
The computer attached to such a system is given the task of correlating all the data received from the sensors in these distinct, small areas, and of producing a table, graph, or other graphic based on the extrapolations of these data. In order for the data to be at all relevant, the computer must make a correlation reading from a sensor located on the outside of the roofing envelope so that it can compare trends in relative humidity on the outside of the roof to the trends being determined by date from the sensors within the roofing envelope. The results are skewed when the temperature changes within the roofing envelope, outside the roofing envelope, or both. The skew is particularly pronounced when temperature changes precipitously, and a certain amount of time is required, sometimes days or weeks, before the system can stabilize enough to produce relevant data again. Even so, relevant data can only be surmised, as the circulation of free air in the roofing envelope cannot be adequately determined, especially across the entire expanse of the envelope. If these systems are retrofitted using tubes inserted into holes cut into the roofing envelope, the temperature sensed in the tubes is different from the actual temperature in the roofing envelope as a whole, and incorrect temperature and the contingent relative humidity measurements are inaccurate, causing false leakage alerts. Further, in order to make such a system more responsive or accurate, sensors must be deployed much closer to one another so the computer will have a greater number of points from which to draw and extrapolate data, driving the cost of the system up. In summary, such systems have significant drawbacks. In addition, the inventor has developed several automatic systems, such as those disclosed in U.S. Pat. Nos. 8,566,051 and 9,341,540 and co-pending U.S. patent application Ser. Nos. 13/442,586, 14/061,480, and 14/107,694, each of which is hereby incorporated by reference.
Another known automatic system requires a grid of hydrophobic cables, the cross-over points of which, when wetted from water flowing through the roofing membrane, make a closed circuit that identifies which portion of the grid is wet and allows location of the leakage through the membrane. This system requires water to make its way to the cross-over points to trigger an alarm and a significant flooding of a portion of the roofing envelope might occur before an alarm is tripped. Such a system is sold under the trademark DETEC.
All of the above named systems require considerable effort on the part of the contractor installing the roofing or waterproofing membrane, as the sensors must be placed within the roofing envelope as the envelope is being constructed, requiring a tremendous amount of coordination between the roofing contractor and the person or firm responsible for installing the sensors. This is because roofing on any project is subject to fits and starts because weather so drastically affects the construction schedule of the roofing envelope.
The most efficient way to build a leak detection system for membrane roofing or waterproofing, therefore, is to have the roofer install the simplest element possible of the leak detection system. In other words, if any part of the leak detection system is performed by the roofing contractor, it will be elements of the system within the roofing envelope, i.e. under the roofing or waterproofing membrane, that are elements that the roofing contractor may already customarily install. In this way, the roofing contractor will not have to deal with any more detail than is necessary to complete the roofing envelope. Thus, a conductive mesh or mat may be placed, just like a roll of roofing, underneath the membrane and within the roofing envelope. The conductive mesh or mat may be made from metal, glass, or plastic and is commonly available in various forms. This involves actions the roofer uses every day a roof is installed. This mesh may be further zoned by electrically isolating a zone or area of the mesh from other zones or areas of the mesh by simply adding a non-conductive strip of roofing or other non-conductive material. Applying strips of membrane or other sheet materials is also something a roofer does on a regular basis.
The sensors are then placed on top of the finished roofing by experienced installers of the leak detection system. This requires minimal involvement from the roofer or other trades, thus assuring that the leak detection system is properly positioned and that the membrane is not penetrated unnecessarily.
This division of labor between general roofing contractors and specialized leak detection system installers provides several advantages: The roofer does not need to be present when the sensors are installed; The sensors and wires may be installed after the roof is finished so that timing of the placement of the system can be coordinated with the last trades working on or around the roof; The sensors may be checked just before application of the overburden, if any.
FIGS. 1A-1C depict a prior art system as described above. The disadvantage of placing sensors on top of the roof is accurately reading the sensors 1. The sensors 1 are placed on top of the roofing membrane 14 and surrounded by a boundary cable (not shown) placed in a loop around the sensors 1. Roofing membrane 14 is disposed on top of a conductive mesh or medium 4. The conductive mesh or medium 4 is placed under the membrane 14 and acts to attract the signal generated by a signal generator (not shown). The system also includes power supply 5. Power supply 5 references sensors 1 to the return side and powers mesh 4. As power supply 5 is common to each, if a leak 6 occurs in the membrane 14, the mesh 4 will complete the circuit and a change in the current will occur and be detected by the sensors 1. The power supply 5 for this system is contained in the computer driven module (not shown) to which the boundary cable and the sensors 1 are connected.
If all goes smoothly, as the sensors 1 and the mesh 4 are connected to the same reference, the sensor 1 that is nearest the breach 6 will read a lower voltage. The location of the breach 6 in the membrane 14 will be able to be triangulated based on the varying voltages detected by the sensors 1 disposed at different distances from the breach 6. This rarely occurs in real-world roofing or waterproofing, however, as there are elements such as stray electrical influences that contribute current to the surface of the roofing or waterproofing membrane 14, either on the bare membrane or in any type of overburden that might later be applied to the surface of the membrane 14. Examples of stray electrical influences 7 include lightning arrestor cables, conduits and vents, lighting on the roof, weather stations on the roof, power sources for devices such as lights and weather stations, anything with a power source, or anything with a transformer. It is known that these stray electrical signals 7 may compromise the discovery of leakage events or locations of leakage 6. Such stray signals 7 may be misinterpreted unless the signal from the leak detection system that generates the readings to locate an actual leak 6 is strong enough to be accurately read despite conflicting or stray signals from other, non-leak detection related elements 7, or is in some other way able to be identified as the real signal.
FIG. 1A is a top down diagram of the system with leak 6 and stray electrical influence 7. FIG. 1C is a side diagram of the same. FIG. 1B is a potential graph, showing the potential measured by various sensors 1 mapped against their location on membrane 14. The solid line 8 shows a graph of potential near actual leak 6. The dashed line 9 shows a graph of potential near stray electrical influence 7. As solid line 8 and dashed line 9 are very similar in both shape and amplitude, it would be very difficult to distinguish which is an actual leak and which is not. In other words, the signal from the leak 6 became contaminated by the stray signal 7 and, instead of lower voltage being read only at sensors 1 near the leak source 6, the voltage rises and falls in more than one area. A contour map of this situation, showing the voltage isopleth, would resemble an area with hills and valleys. FIG. 1B is a two-dimensional example, or cross section of such a map. These hills and valleys make isolating the location of the actual leak 6 extremely difficult, if not impossible.
It is possible to isolate the leak 6 manually, using an electrical balance in a process called ‘vector mapping’, in which two poles, one held in each hand, are connected to a balanced electrical meter so that minute changes in voltage are detected, and the needle of the meter swings toward the side that has a lower voltage. This process can easily lead a trained technician to the leak 6 as long as the technician accounts for any stray signals 7 as he or she is working the method. This is in part because the poles are held only a small distance apart, usually less than 4 feet, so compensation for stray signals 7 can be accomplished by trial and error, i.e. by moving the poles on different axes.
In an effort to eliminate the need for such manual testing, it would be possible to construct an automatic real-time leak detection that has a distance between sensors of less than 4 feet. However, it is not practical to build such tight systems in reality and further, the axis of any chain of sensors cannot be changed once the sensors are secured to the membrane.
Another element that limits the effectiveness of reading sensors 1 on top of the membrane 14 is the weather, which provides wetter and drier periods. Such weather variations may skew the readings to some extent, and because the source of the current is the boundary cable located on the perimeter of the test area, the boundary cable must be wet in order to transmit the current to the sensors in the test field. Further, any discontinuance of moisture on the surface of the membrane will affect the readings of the sensors 1 if the discontinuity of the moisture blocks the signal from the boundary cable.
It is a known fact that the overburden that covers a membrane system might allow water to flow to the membrane in some places, but not in others, resulting in an uneven distribution of water at the membrane surface. It is further known that the surface upon which the membrane system is applied can be uneven, resulting in areas of water accumulation known as ponding. Both of these conditions may change the signature of the signal generated by a boundary cable and skew the interpretation of the data acquired from manual and automatic leak location systems. If the membrane is bare, these conditions may be accommodated. After application of the overburden, however, these conditions may not be verified from the surface of the overburden that has variable areas of dry or wet and conducting or not conducting. Determining leakage from the top of the overburden or from the sensors in a system in which the boundary cable is responsible for current generation therefore becomes much more difficult.
Another problem that roofing and waterproofing systems have is that edges and penetrations account for most of the leakage in the membrane system. This is because of the amount of careful hand work required to effect the waterproofing, or flashing, of walls, vents, curbs and the like. Automatic real-time leak detection systems have struggled to determine leakage at these elements, primarily because the flashings rise and are vertical, laid against a curb, wall or stack, or the flashings are flat flanges, welded to the flat of the membrane. There was no way until the present invention of determining when and where leakage could occur in flashings.
The present invention endeavors to overcome the limitations as discussed above.